1. Field of the Invention
The present invention relates to aqueous dispersions or solutions of compositions containing compounds, which contain alkoxysilane and/or silanol groups, and colloidal silica to increase the pot life, and to their use as binders for coating, adhesive or sealant compositions.
2. Description of the Prior Art
Compounds containing urea or hydantoin groups and also containing alkoxysilane groups are known and disclosed in U.S. Pat. Nos. 5,756,751 and 5,364,955. The presence of alkoxysilane groups in these compounds can be used to improve the adhesion and chemical resistance properties of coatings when compared to those prepared from the known polyurethane resins. One of the disadvantages of these compounds is the need to blend them with organic solvents in order to reduce their viscosity for certain applications.
Applications, U.S. Ser. No. 08/992,163, now U.S. Pat. No. 5,932,652, Ser. No. 08/992,551, now U.S. Pat. No. 5,919,860, and Ser. No. 09/057,675, now U.S. Pat. No. 5,952,445, disclose that it is possible to reduce or eliminate the need for organic solvents by dispersing the compounds containing alkoxysilane groups in water. However, in order to render these compounds water dispersible it is necessary to hydrophilically modify these aqueous compositions by chemically incorporating ionic and/or non-ionic hydrophilic groups and optionally by the use of external emulsifiers.
While the presence of the hydrophilic groups improves the compatibility of the urea/hydantoin compounds with water, it also makes the coatings, adhesives or sealants prepared from these compounds more sensitive to water or moisture. In particular, the water resistance of the resulting products is reduced and the amount of water swelling that the products undergo in the presence of water is increased.
These deficiencies were overcome in copending application Ser. No. 09/221,032, which describes aqueous compounds containing alkoxysilane and/or silanol groups that did not require the known ionic and/or non-ionic hydrophilic groups to render the compounds water soluble or dispersible. One of the disadvantages of these aqueous compositions is that their pot life is too short for certain applications.
Accordingly, it is an object of the present invention to increase the pot life of the aqueous compounds disclosed in the copending application.
This object may be achieved in accordance with the present invention by mixing the aqueous compounds of the copending application with colloidal silica as described hereinafter.